<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <div id="root"></div>
</body>
</html>
<script src="https://unpkg.com/vue@next"></script>
<script>
    const app = Vue.createApp({
        data(){
            return{
                count:1,
            }
        },
        methods:{
            handleAdd(count){
                this.count += count;
            }
        },
        template:`
        <div>
            <counter :count="count" @add="handleAdd" />
        </div>
        `
    });
    app.component('counter',{
        props:['count'],
        emits:['add'],
        methods:{
            handleClick(){
                this.$emit('add',this.count+3);
            }
        },
        template:`
        <div @click="handleClick">{{count}}</div>
        `
    })
    const vm = app.mount('#root')
</script>